Notes Payable (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2018

Dec. 31, 2017

Debt Disclosure [Abstract]

Schedule of Notes Payable

Notes payable consists of the following:

	March 31, 2018		December 31, 2017
	(In millions)
Unsecured notes, net of discount, interest payable semi-annually at 5.50%, due September 2022	$	398	$	397
Unsecured convertible notes, net of discount, interest payable semi-annually at 4.25%, due August 2018	53		65
Revolving Credit Facility, unsecured, unused portion of $500, due April 2022 with interest payable quarterly at LIBOR + 1.40% (3.12% at March 31, 2018)	295		295
Other	2		2
	$	748	$	759

Notes payable consists of the following:

	December 31,
	2017		2016
	(In millions)
Unsecured notes, net of discount, interest payable semi-annually at 5.50%, due September 2022	$	397	$	397
Unsecured convertible notes, net of discount, interest payable semi-annually at 4.25%, due August 2018	65		291
Unsecured notes, net of discount, interest payable semi-annually at 6.60%, due May 2017	—		300
Revolving Credit Facility, unsecured, unused portion of $500 at December 31, 2017, due April 2022 with interest payable monthly at LIBOR + 1.40% (2.76% at December 31, 2017)	295		(3		)
Other	2		2
	$	759	$	987

Schedule of Maturities of Notes Payable

Gross principal maturities of notes payable at March 31, 2018 are as follows (in millions):
2018 (remaining)	$	54
2019	—
2020	1
2021	—
2022	700
Thereafter	—
	$	755

Gross principal maturities of notes payable at December 31, 2017 are as follows (in millions):
2018	$	66
2019	—
2020	1
2021	—
2022	700
Thereafter	—
	$	767